Self-screening of the particle-hole interaction and core polarization of the effective two-particle interaction

Abstract

The diagrams of the Tamm-Dancoff and random-phase approximations (TDA and RPA) have been summed to calculate the core polarization of the effective interaction between two nucleons in the 1s0d and Ip0f shells. The large core-polarization corrections obtained in the TDA and particularly the RPA are strongly reduced when the self-screening corrections to the particle-hole and ground-state correlation vertices are included. The screening corrections serve to suppress the collectivity of the core phonons and in particular stabilize the isoscalar monopole phonon in 40Ca against collapse. When screening is included the TDA and RPA give core-polarization corrections which are similar in magnitude and in many cases lead to good agreement with experiment. Because of neglected effects and other uncertainties the qualitative rather than the quantitative features of the results are stressed.